Preparation and characterization of different supported 4-n-butylresorcinol nanoemulsions

Abstract 4-n-butylresorcinol (4-nBR) has a significant effect on skin pigmentation, but its poor solubility, low stability and strong irritation to the skin limit its application. In this study, 4-nBR was prepared into 4-n-butylresorcinol nanoemulsion (4-nBR-NE) for the first time, which improved the solubility and stability of 4-nBR and greatly reduced the irritation of 4-nBR on skin. On this basis, the relationship between the viscosity of nanoemulsion and the formulation process, and the relationship between the ratio of surfactant and the formability of 4-nBR-NE were further studied. A nanoemulsion with adjustable viscosity (AV-NE) and nanoemulsion with low surfactant content has been successfully developed. The particle size of 4-nBR-NE was 13.34 ± 0.1646 nm, and PDI (0.08532 ± 0.0191) was small, and the particle size distribution was uniform. The encapsulation rate of 4-nBR-NE was 80.05 ± 0.75% by UV-VIS spectrophotometry. In addition, 4-nBR-NE had excellent stability for several months that the particle size was almost unchanged. We also confirmed through cells and transdermal evaluations that the original irritation of 4-nBR on cells and skin could be effectively reduced after preparation of 4-nBR-NE. Then 4-nBR-NE was prepared into essence. TEM showed that the shape of the 4-nBR-NE could still be observed after the essence was prepared, indicating that the shape of the 4-nBR-NE could still be maintained when the 4-nBR-NE was added to other products as an intermediate. In summary, 4-nBR-NE could not only improve the stability, solubility and transdermal delivery efficiency of 4-nBR, but also effectively reduce the original irritation of 4-nBR, which can be used to help treat pigmentation, melasma, freckles and other skin diseases. 4-nBR has increased its applicability in the pharmaceutical and cosmetic industries.